The present invention relates generally to control systems for internal combustion engines, and more particularly, to an electronic throttle servo hard stop relearning system.
Many previously known motor vehicle throttle control systems have a direct physical linkage between an accelerator pedal and the throttle body so that the throttle plate is pulled open by the accelerator cable as the driver presses the pedal. The direct mechanical linkages include a biasing force that defaults the linkage to a reduced operating position, in a manner consistent with regulations. Nevertheless, such mechanisms are often simple and unable to adapt fuel consumption efficiency to changing traveling conditions. Moreover, these mechanisms add significant weight and components to the motor vehicle.
An alternative control for improving throttle control and the efficient introduction of fuel air mixtures into the engine cylinders is presented by electronic throttle control. The electronic throttle control includes a throttle control unit that positions the throttle plate by an actuator controlled by a microprocessor based on the current operating state determined by sensors. The processors are often included as part of a powertrain electronic control that can adjust the fuel air intake and ignition in response to changing conditions of vehicle operation as well as operator control. Protection may be provided so that an electronic system does not misread or misdirect the control and so that unintended operation is avoided when portions of the electronic control suffer a failure.
Typically, the actuator or servomotor used to position the throttle plate is designed to have the maximum control effort available (motor voltage, current, duty cycle) to enhance throttle plate position response. Having a large control effort continuously available or available for maximum effort could possibly lead to overstressing the system""s physical components if a blockage of the throttle plate occurs or if the throttle is commanded to a mechanical limit, such as the close stop or open stop. Specifically, the H-driver and the servomotor could overheat with sustained full control effort under some environmental conditions. In an effort to avoid permanent damage, most electronic systems shut down when they get to a threshold temperature.
Additionally, typical prior art electronic throttle controllers only learn the closed stop position upon power-up or power-down of the throttle controller.
The disadvantages associated with these conventional electronic throttle overheat protection techniques have made it apparent that a new technique for electronic throttle overheat protection is needed. The new technique should allow full control effort while preventing overheat conditions. Additionally, the new technique should continuously learn the open stop position and the close stop position to prevent the throttle plate from striking a detent at high speed, thereby risking damage to the device. Detecting on-line compensates for variations in detent location due to thermal expansion, thermal contraction, and thermal drift in the feedback source, the throttle position sensors. The present invention is directed to these ends.
It is, therefore, an object of the present invention to provide an improved and reliable electronic throttle servo temperature protection system. Another object of the present invention is to allow full control effort while preventing overheat conditions. Additionally, the present invention should continuously learn the closed stop position. It is yet another object of the present invention to detect the mechanical limits not only at power up or power down, but also online.
In accordance with the above and other objects of the present invention, an electronic throttle servo hard stop relearning system is provided. In one embodiment of the invention, a method for controlling a positioning device of an internal combustion engine is provided. The method includes providing an electric motor for actuating the positioning device. The positioning device is commanded to change to a commanded position. A control effort required to change to the commanded position is then detected. Thereafter, whether the control effort exceeds a threshold for a predetermined time period is determined. The control effort is reduced when the control effort exceeds the threshold for the predetermined time period. Each full stop position is relearned each time such stop is commanded for a given duration.
The present invention thus achieves an improved electronic throttle servo hard stop detection system system. The present invention is advantageous in that it will not cause mechanism failure or require significant and costly added robustness to the mechanism.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.